1. Field of the Invention
The present invention relates to a power semiconductor device having a structure in which at least one discrete semiconductor device is disposed in a case.
2. Description of the Background Art
In a background-art power semiconductor device, a resin-sealed power semiconductor element is mounted on a cooling fin with grease interposed therebetween, to radiate the heat of the power semiconductor element (see e.g., Patent Document 1).
 less than Patent Document 1 greater than  Japanese Patent Application Laid Open Gazette No. 2001-250911.
The background-art power semiconductor device, however, has a problem that it is impossible to ensure sufficient heat radiation since the thermal conductivity of grease is low.
Further, since the flatness of a surface for mounting the fin has a great influence on the heat radiation, the fin mounting surface needs high-level flatness and this raises a problem that the manufacturing cost increases.
It is an object of the present invention to provide a power semiconductor device which allows an increase in radiating efficiency of a power semiconductor element and reduction in manufacturing cost.
The present invention is intended for a power semiconductor device. According to the present invention, the power semiconductor device includes a hollow case and a discrete semiconductor device having a terminal for external connection. The discrete semiconductor device is fitted in the case to be positioned and disposed on a predetermined portion inside the case with the terminal protruding outside from the case. A space defined by a surface of the discrete semiconductor device and an inner wall of the case forms a duct for a coolant used for cooling the discrete semiconductor device which is immersed therein.
The discrete semiconductor device is immersed in the coolant. Therefore, the discrete semiconductor device can be directly cooled by the coolant and this enhances the cooling efficiency of the discrete semiconductor device.
Further, the discrete semiconductor device is fitted in the case to be positioned and disposed on a predetermined portion inside the case. This enhances the mounting accuracy of a control circuit substrate and the like.
These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.